Method for transmitting data frame in wireless local area network and apparatus for the same

ABSTRACT

A wireless device of transmitting a data frame in a WLAN is provided. The wireless device includes: a MAC unit generating a data frame; a PHY unit transmitting a wireless signal of the data frame; and a processor being operably coupled to the MAC unit and the PHY unit and controlling a set of TXVECTOR parameters. The processor is configured for: generating the data frame, the data frame including a data field having a service field and a very high throughput signal information (VHT-SIG-B); and transmitting a wireless signal of the data frame via a operating channel bandwidth. The data field is scrambled with a scrambling sequence, the scrambling sequence is generated based on a initial scrambling sequence and a generator polynomial. The service field is determined based on the set of TXVECTOR parameters, the TXVECTOR parameters including an control information for the service field.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of Korean PatentApplications No. 10-2011-0044805 filed on May 12, 2011, and No.10-2012-0050431 filed on May 11, 2012, all of which are incorporated byreference in their entirety herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless local area network (WLAN)system, and more particularly, to a method for transmitting a data frameby a sender in a WLAN system and an apparatus for supporting the same.

2. Related Art

Recently, various wireless communication technologies are underdevelopment in accordance with the advancement of an informationcommunication technology. Among them, a wireless local area network(WLAN) is a technique of wirelessly accessing the Internet at homes, inoffices, or in a particular service providing area, using portableterminals such as personal digital assistants (PDAs), lap top computers,portable multimedia players (PMPs), and the like, based on a radiofrequency technology.

As a technology specification that has been relatively recentlylegislated in order to overcome a limitation in a communication speedthat has been pointed out as a weak point in the WLAN, there is the IEEE802.11n. An object of the IEEE 802.11n is to increase a speed andreliability of a wireless network and extend an operating distance ofthe wireless network. More specifically, the IEEE 802.11n is based on amultiple input and multiple output (MIMO) technology in which multipleantennas are used at both of a transmit end and a receive end in orderto support a high throughput (HT) having a maximum data processing speedof 540 Mbps or more, minimize a transmission error, and optimize a datarate.

As the supply of the WLAN is activated and applications using the WLANis diversified, the necessity for a new WLAN system for supporting athroughput higher than a data processing speed supported by the IEEE802.11n has recently increased. The next generation WLAN systemsupporting a very high throughput (VHT) is the next version of the IEEE802.11n WLAN system and is one of the IEEE 802.11 WLAN systems that havebeen newly suggested recently in order to support a data processingspeed of 1 Gbps or more in a MAC service access point (SAP).

The next generation WLAN system supports transmission in a multi-usermultiple input multiple output (MU-MIMO) scheme in which a plurality ofnon-AP STAs simultaneously accesses wireless channels in order toefficiently use the wireless channels. According to the MU-MIMOtransmission scheme, an AP may simultaneously transmit frames to one ormore MIMO paired station (STA).

The next generation WLAN system may support 80 MHz, contiguous 160 MHz,non-contiguous 80+80 MHz, and a channel bandwidth higher than theabove-mentioned bandwidth in order to support a higher throughput. Inaddition, the next generation WLAN system supports a transceiving schemeof a duplicated data unit. In this case, the next generation WLAN systemmay support dynamic bandwidth operation. In connection with functionsthat may be supported in the next generation WLAN system as describedabove, a method for processing data that a transmit STA is to transmitand transmitting the data, a method for normally receiving thetransmitted data in a receive STA, and an apparatus for supporting thesame, has been demanded.

SUMMARY OF THE INVENTION

The present invention provides a method for transmitting a data frame ina wireless local area network (WLAN) system and an apparatus forsupporting the same.

In an aspect, a wireless device of transmitting a data frame in awireless local area network is provided. The wireless device includes: amedia access control (MAC) unit generating a data frame; a physical(PHY) unit transmitting a wireless signal of the data frame; and aprocessor being operably coupled to the MAC unit and the PHY unit andcontrolling a set of TXVECTOR parameters. The processor is configuredfor: generating the data frame, the data frame including a data fieldhaving a service field and a very high throughput signal information(VHT-SIG-B); and transmitting a wireless signal of the data frame via aoperating channel bandwidth. The data field is scrambled with ascrambling sequence, the scrambling sequence is generated based on ainitial scrambling sequence and a generator polynomial. The servicefield is determined based on the set of TXVECTOR parameters, theTXVECTOR parameters including an control information for the servicefield.

The control information may indicate a format of the service field. Ifthe control information indicates the format of the service field asvery high throughput (VHT), the service field may include a scramblerinitialization, a reserved field and a cyclic redundancy check (CRC).

The VHT-SIG-B may include length field and tail bits.

The cyclic redundancy check (CRC) may be calculated based on theVHT-SIG-B excluding the tail bits.

The scrambler initialization may have 7 bits, the reserved field mayhave 1 bit and cyclic redundancy check (CRC) may have 8 bits.

The initial scrambling sequence may include operating channel bandwidthinformation and a pseudo random integer, the operating channel bandwidthindicating the operating channel bandwidth.

The initial scrambling sequence may further include dynamic bandwidthinformation indicating whether a dynamic bandwidth operation issupported.

The operating channel bandwidth information may have 2 bits.

The 2 bits may indicate one among 20 MHz, 40 MHz, 80 MHz, contiguous 160MHz and non-contiguous 80+80 MHz for the operating channel bandwidth.

The initial scrambling sequence may have 7 bits.

The generator polynomial may be represented by the below formula,S(x)=x⁷+x⁴+1.

In another aspect, a method for transmitting a data frame in a wirelesslocal area network is provided. The method includes: generating a dataframe, the data frame including a data field having a service field anda very high throughput signal information (VHT-SIG-B); and transmittinga wireless signal of the data frame via a operating channel bandwidth.The data field is scrambled with a scrambling sequence, the scramblingsequence is generated based on a initial scrambling sequence and agenerator polynomial. The service field is determined based on a set ofTXVECTOR parameters, the TXVECTOR parameters including an controlinformation for the service field.

The control information may indicate a format of the service field. Ifthe control information indicates the format of the service field asvery high throughput (VHT), the service field may include a thescrambler initialization, a reserved field and a cyclic redundancy check(CRC).

The VHT-SIG-B may include length field and tail bits.

The CRC may be calculated based on the VHT-SIG-B excluding the tailbits.

The scrambler initialization may have 7 bits, the reserved field mayhave 1 bit and the CRC may have 8 bits.

The initial scrambling sequence may include operating channel bandwidthinformation and a pseudo random integer, the operating channel bandwidthinformation indicating the operating channel bandwidth.

The initial scrambling sequence may further include a dynamic bandwidthinformation indicating whether a dynamic bandwidth operation issupported.

The operating channel bandwidth information may have 2 bits.

The 2 bits may indicate one among 20 MHz, 40 MHz, 80 MHz, contiguous 160MHz and non-contiguous 80+80 MHz for the operating channel bandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of a wireless local areanetwork (WLAN) system to which an exemplary embodiment of the presentinvention may be applied.

FIG. 2 is diagram showing a physical layer architecture of a WLAN systemsupported by the IEEE 802.11.

FIG. 3 is a diagram showing an example of a PPDU format used in the WLANsystem.

FIG. 4 is a block diagram showing a format of a data field according tothe exemplary embodiment of the present invention.

FIG. 5 is a diagram showing an example of a method for transmitting adata unit based on a method for generating a PPDU according to theexemplary embodiment of the present invention.

FIG. 6 is a diagram showing an example of scrambling according to theexemplary embodiment of the present invention.

FIG. 7 is a diagram showing an example of an initial scrambling sequenceaccording to the exemplary embodiment of the present invention.

FIG. 8 is a diagram showing an example of a method for receiving a PPDUgenerated according to the exemplary embodiment of the presentinvention.

FIG. 9 is a block diagram showing a wireless apparatus to which theexemplary embodiment of the present invention may be implemented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 is a diagram showing a configuration of a wireless local areanetwork (WLAN) system to which an exemplary embodiment of the presentinvention may be applied.

The WLAN system includes one or more basic service set (BSS). The BSS,which is a set of stations (STAs) that may be successfully synchronizedwith each other to communicate with each other, is not the concept ofmeaning a specific region.

An infrastructure BSS includes one or more non-AP station (STA), anaccess point (AP) 10 providing a distribution service, and adistribution system (DS) connecting a plurality of APs to each other. Inthe infrastructure BSS, the AP manages the non-AP STAs of the BSS.

On the other hand, an independent BSS (IBSS) is a BSS operating in anAd-Hoc mode. Since the IBSS does not include the AP, it does not have acentralized management entity. That is, in the IBSS, the non-AP STAs aremanaged in a distributed manner. In the IBSS, all STAs may be mobileSTAs, and an access to DS is not allowed, such that a self-containednetwork is formed.

The STA, which is any functional medium including a medium accesscontrol (MAC) according to the Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 standard specification and a physical layerinterface for a wireless medium, includes both of AP and non-AP stationsin a broad sense.

The non-AP STA, which is an STA that is not the AP, may also be referredto as other names such as a mobile terminal, a wireless device, awireless transmit/receive unit (WTRU), a user equipment (UE), a mobilestation (MS), a mobile subscriber unit, or simply, a user, and the like.Hereinafter, the non-AP STA will be referred to as an STA forconvenience of explanation.

The AP is a functional medium providing an access to the DS through awireless medium for an STA associated with a corresponding AP. In theinfrastructure BSS including the AP, communication between the STAs isperformed through the AP in principle. However, in the case in which adirect link is set, direct communication between the STAs may also beperformed. The AP may also be referred to as a central controller, abase station (BS), a node-B, a base transceiver system (BTS), a sitecontroller, and the like.

A plurality of infrastructure BSSs including a BSS shown in FIG. 1 maybe connected to each other through a distribution system (DS). Theplurality of BSSs connected to each other through the DS is called anextended service set (ESS). An AP 10 and/or STAs 21, 22, 23, 24, and 30included in the ESS may communicate with each other, and the STA maymove from one BSS to another BSS while performing seamlesscommunication.

In a WLAN system according to the IEEE 802.11, a basic access mechanismof a medium access control (MAC) is a carrier sense multiple access withcollision avoidance (CSMA/CA) mechanism. The CSMA/CA mechanism, which isalso called a distributed coordination function (DCF) of the IEEE 802.11MAC, basically adopts a “listen before talk” access mechanism. Accordingto this type of access mechanism, the AP and/or the STA senses awireless channel or a medium before starting transmission. As a resultof the sensing, when it is determined that the medium is in an idlestatus, the AP and/or the STA starts frame transmission through thecorresponding medium. On the other hand, it is determined that themedium is in an occupied status, the corresponding AP and/or STA doesnot start it's transmission, but sets a delay time for a medium accessto thereby wait.

The CSMA/CA mechanism also includes virtual carrier sensing, in additionto physical carrier sensing in which the AP and/or the STA directlysenses the medium. The virtual carrier sensing is to complement aproblem that may be generated in view of a medium access, such as ahidden node problem. In order to perform the virtual carrier sensing,the MAC of the WLAN system uses a network allocation vector (NAV). TheNAV is a value notifying other APs and/or STAs of a remaining time untilan AP and/or an STA that is currently using a medium or is authorized touse the medium is in a state in which it may use the medium. Therefore,the value set to the NAV corresponds to a period in which the medium isscheduled to be used by the AP and/or the STA transmitting acorresponding frame.

The IEEE 801.11 MAC protocol provides a hybrid coordination function(HCF) based on the DCF and a point coordination function (PCF) ofperforming periodic polling so that all receive APs and/or STAs mayreceive data packets in a polling based synchronous access scheme. TheHCF has a HCF controlled channel access (HCCA) using a contention basedenhanced distributed channel access (EDCA) and a contention free basedchannel access scheme using a polling mechanism as an access scheme inwhich a provider provides the data packets to a plurality of users. TheHCF may include a medium access mechanism for improving quality ofservice (QoS) of the WLAN and the AP and/or the STA may transmit QoSdata in both of a contention period (CP) and a contention free period(CFP).

The AP and/or the STA may perform a procedure of exchanging a request tosend (RTS) frame and a clear to send (CTS) frame in order to inform themedium that it is to access the medium. The RTS frame and the CTS frameinclude information indicating a temporal section reserved to access awireless medium required for transceiving an acknowledgement frame (ACKframe) in the case in which substantial data frame transmission andreception acknowledgement is supported. Another STA receiving a RTSframe transmitted from an AP and/or an STA that is to transmit a frameor receiving a CTS frame transmitted from a frame transmission targetSTA may be set so as not to access a medium during a temporal sectionindicated by information included in the RTS/CTS frames. This may beimplemented by setting the NAV during the temporal section.

FIG. 2 is diagram showing a physical layer architecture of a WLAN systemsupported by the IEEE 802.11.

The wireless-medium physical layer (PHY) architecture of the IEEE 802.11includes a PHY layer management entity (PLME), a physical layerconvergence procedure (PLCP) sub-layer 210, a physical medium dependent(PMD) sub-layer 200. The PLME provides a management function of thephysical layer in cooperation with a MAC layer management entity (MLME).The PLCP sub-layer 210 transfers an MAC protocol data unit (MPDU)received from an MAC sub-layer 220 to a PMD sub-layer 200 or transfers aframe coming from the PMD sub-layer 200 to the MAC sub-layer 220according to instruction of the MAC layer, between the MAC sub-layer 220and the PMD sub-layer 200. The PMD sub-layer 200, which is a lower layerof the PLCP, may allow a physical layer entity to be transmitted andreceived between two stations through a wireless medium. The MPDUtransferred from the MAC sub-layer 220 is called a physical service dataunit (PSDU) in the PLCP sub-layer 210. The MPDU is similar to the PSDU.However, when an aggregated MPDU (A-MPDU) formed by aggregating aplurality of MPDUs is transferred, individual MPDUs and PSDUs may bedifferent.

The PLCP sub-layer 210 adds an additional field including informationrequired by a physical layer transceiver to the PSDU during a process ofreceiving the PSDU from the MAC sub-layer 220 and transferring the PSDUto the PMD sub-layer 200. Here, the field added to the PSDU may be aPLCP preamble, a PLCP header, tail bits required to return aconvolutional encoder to a zero state, or the like. The PCLP sub-layer210 receives a TXVECTOR parameter including control information requiredto generate and transmit a PPDU and control information required for areceive STA to receive and interpret the PPDU, from the MAC sub-layer.The PLCP sub-layer 210 uses the information included in the TXVECTORparameter in generating the PPDU including the PSDU.

The PLCP preamble serves to allow a receiver to prepare asynchronization function and antenna diversity before the PSDU istransmitted. The data field may include a coded sequence formed byencoding a bit sequence in which padding bits, a service field includinga bit sequence for initializing a scrambler, and tail bits are added tothe PSDU. Here, an encoding scheme may be one of a binary convolutionalcoding (BCC) encoding and a low density parity check encoding (LDPC)according to an encoding scheme supported by a STA receiving the PPDU.The PLCP header includes a field including information on a PLCPprotocol data unit (PPDU) to be transmitted, which will be describedbelow in more detail with reference to FIG. 3.

In the PLCP sub-layer 210, the above-mentioned field is added to thePSDU to generate the PLCP protocol data unit (PPDU) and transmit thePPDU to the receive station through the PDM sub-layer, and the receivestation receives the PPDU and acquires information required toreconstruct data from the PLCP preamble and the PLCP header toreconstruct the data. The PLPC sub-layer of the receive stationtransfers an RXVECTOR parameter including the control informationincluded in the PLPC preamble and the PLCP header to the MAC sub-layerto allow the PPDU to be interpreted and data to be acquired in areception station.

Unlike an existing WLAN system, the next generation WLAN system requiresa higher throughput. This is called a very high throughput (VHT). Tothis end, the next generation WLAN system is to support transmission in80 MHz, contiguous 160 MHz, non-contiguous 80+80 MHz, and/or a bandwidthhigher than the above-mentioned bandwidth. Further, the next generationWLAN system provides a multi-user multiple input multiple output(MU-MIMO) transmission method in order to provide higher throughput. Inthe next generation WLAN system, the AP may simultaneously transmit thedata frame to at least one MIMO paired STA.

In the WLAN system as shown in FIG. 1, the AP 10 may simultaneouslytransmit the data to a STA group including at least one of the pluralityof STAs 21, 22, 23, 24, and 30 associated therewith. Although the casein which the AP 10 performs the MU-MIMO transmission to the STAs 21, 22,23, 24, and 30 is shown by way of example in FIG. 1, in a WLAN systemsupporting a tunneled direct link setup (TDLS), a direct link setup(DLS), or a mesh network, a STA that is to transmit data may transmit aPPDU to a plurality of STAs using the MU-MIMO transmission scheme.Hereinafter, the case in which the AP transmits the PPDU to theplurality of STAs using the MU-MIMO transmission scheme will bedescribed by way of example.

The data transmitted to each STA may be transmitted through differentspatial streams. The data frame transmitted by the AP 10 may be referredto as a PPDU generated and transmitted in a physical layer (PHY) of theWLAN system. In an example of the present invention, it is assumed thata transmission target group MU-MIMO paired with the AP 10 is a STA1 21,a STA2 22, a STA3 23, and a STA4 24. Here, the spatial stream is notallocated to a specific STA in the transmission target STA group, suchthat the data may not be transmitted thereto. Meanwhile, it is assumedthat a STAa 30 is a STA that is associated with the AP but is notincluded in the transmission target STA group.

In the WLAN system, the transmission target STA group may be allocatedwith an identifier, which is called a group identifier (Group ID). TheAP transmits a group ID management frame including group definitioninformation to the STAs supporting the MU-MIMO transmission in order toallocate the group ID thereto, such that the group ID is allocated tothe STAs before transmission of the PPDU. One STA may be allocated witha plurality of group IDs.

The following Table 1 shows information elements included in a group IDmanagement frame.

TABLE 1 Order Information 1 Category 2 VHT Action 3 Membership Status 4Spatial Stream Position

A category field and a VHT action field are set so that it may beidentified that a corresponding frame corresponds to a management frameand is a group ID management frame used in the next generation WLANsystem.

As shown in Table 1, the group definition information includesmembership status information indicating whether or not a specific STApertains to a specific group ID and spatial stream position informationindicating whether a spatial stream set of the specific STA correspondsto the n-th position in the entire spatial stream according to theMU-MIMO transmission in the case in which the specific STA pertains tothe specific group ID.

Since a single AP manages a plurality of group IDs, the membershipstatus information provided to a single STA needs to indicate whether ornot the STA pertains to each of the group IDs managed by the AP.Therefore, the membership status information may be present in a form ofan array of sub-fields indicating whether the STA pertains to each groupID. Since the spatial stream position information indicates positionsfor each of the group IDs, it may be present in a form of an array ofsub-fields indicating a position of a spatial stream set occupied by theSTA for each of the group IDs. In addition, the membership statusinformation and the spatial stream position information for a singlegroup ID may be implemented in a single sub-field.

In the case in which the AP transmits the PPDU to the plurality of STAsthrough the MU-MIMO transmission scheme, it allows informationindicating the group ID to be included in the PPUD as controlinformation and then transmit the PPDU. When the STA receives the PPDU,it confirms a group ID field to confirm whether the STA is a member STAin the transmission target STA group. It is confirmed that the STA isthe member STA in the transmission target STA group, the STA may confirmwhether the spatial stream set transmitted to the STA is positioned atthe n-th position in the entire spatial stream. Since the PPDU includesinformation on the number of spatial streams allocated to the receiveSTA, the STA may search the spatial streams allocated thereto to receivethe data.

FIG. 3 is a diagram showing an example of a PPDU format used in the WLANsystem.

Referring to FIG. 3, the PPDU 300 may include L-STF 310, L-LTF 320, anL-SIG field 330, a VHT-SIGA field 340, VHT-STF 350, VHT-LTFs 360,VHT-SIGB fields 370, and data fields 380.

The PLCP sub-layer configuring the PHY adds required information to thePSDU received from the MAC layer to convert the PSDU into the data field380, and adds fields such as the L-STF 310, the L-LTF 320, the L-SIGfield 330, the VHT-SIGA field 340, the VHT-STF 350, the VHT-LTF 360, andthe VHT-SIGB field 370, and the like, to the data field 380 to generatethe PPDU 300 and transmit the PPDU 300 to one or more STA through thePMD sub-layer configuring the PHY. The control information required forthe PLCP sub-layer to generate the PPDU is provided from the TXVECTORparameter received from the MAC layer. Meanwhile, the controlinformation used for the receive STA to receive and interpret the PPDUis provided from the RXVECTOR parameter based on the control informationincluded in the PLCP header of the PPDU.

The L-STF 310 is used for frame timing acquisition, automatic gaincontrol (AGC) convergence, coarse frequency acquisition, or the like.

The L-LTF 320 is used for channel estimation for demodulation of theL-SIG field 330 and the VHT-SIGA field 340.

The L-SIG field 330 is used for an L-STA to receive and interpret thePPDU 300 to acquire the data. The L-SIG field 330 includes a ratesub-field, a length sub-field, a parity bit, and a tail field. The ratesub-field is set to a value indicating a bit rate for data that iscurrently to be transmitted.

The length sub-field is set to a value indicating an octet length of thePSDU that the MAC layer requests the PHY layer to transmit. Here, anL_LENGTH parameter which is a parameter related to information on theoctet length of the PSDU is determined based on an TXTIME parameterwhich is a parameter related to a transmission time. The TXTIMEindicates a transmission time determined by the PHY layer fortransmission of the PPDU including PSDU in response to a transmissiontime requested by the MAC layer for transmission of the PSDU. Therefore,since the L_LENGTH parameter is a parameter related to a time, thelength sub-field included in the L-SIG field 330 includes informationrelated to the transmission time.

The VHT-SIGA field 340 includes control information (or signalinformation) required for the STAs receiving the PPDU 300 to interpretthe PPDU 300. The VHT-SIGA field 340 is transmitted as two OFDM symbols.Therefore, the VHT-SIGA field 340 may be divided into a VHT-SIGA1 fieldand a VHT-SIGA2 field. The VHT-SIGA1 field includes channel bandwidthinformation used for transmitting the PPDU, identification informationrelated to whether or not space time block coding (STBC) is used,information indicating a scheme (SU-MIMO or MU-MIMO) in which the PPDUis transmitted, information indicating the transmission target STA groupwhich is a plurality of STAs MU-MIMO paired with the AP when thetransmission method is the MU-MIMO, and information on the spatialstreams allocated to each STA included in the transmission target STAgroup. The VHT-SIGA2 field includes information related to a short guardinterval (GI).

The information indicating the MIMO transmission scheme and theinformation indicating the transmission target STA group may beimplemented by single MIMO indication information, for example, a groupID. The group ID may be set to a value having a specific range, aspecific value of which indicates the SU-MIMO transmission scheme andother values may be used as an identifier for a correspondingtransmission target STA group in the case in which the PPDU 300 istransmitted by the MU-MIMO transmission scheme.

When the group ID indicates that the corresponding PPDU 300 istransmitted by the SU-MIMO transmission scheme, the VHT-SIGA2 fieldincludes information indicating whether a coding scheme applied to thedata field is binary convolutional coding (BCC) or low density paritycheck (LDPC) coding and modulation coding scheme (MCS) information on achannel between a sender and a receiver. In addition, the VHT-SIGA2field includes an AID of the transmission target STA of the PPDU and/ora partial AID including a partial bit sequence of the AID.

When the group ID indicates that the corresponding PPDU 300 istransmitted through the MU-MIMO transmission scheme, the VHT-SIGA field300 includes coding indication information indicating whether a codingscheme applied to a data field that is intended to be transmitted to theMU-MIMO paired receive STAs is the BSS or the LDPC coding. In this case,MCS information on each receive STA may be included in the VHT-SIGBfield 370.

The VHT-STF 350 is used to improve performance of AGC estimation in theMIMO transmission.

The VHT-LTE 360 is used for the STA to estimate an MIMO channel. Sincethe next generation WLAN system supports the MU-MIMO, the VHT-LTFs 360may be set to the number corresponding to the number of spatial streamsthrough which the PPDU 300 is transmitted. Additionally, full channelsounding is supported. In the case in which the full channel sounding isperformed, the number of VHT LTEs may increase.

The VHT-SIGB field 370 includes dedicated control information requiredfor the plurality of MIMO paired STAs to receive the PPDU 300 to acquirethe data. Therefore, the STA may be designed so as to decode theVHT-SGIB field 370 only in the case in which common control informationincluded in the VHT-SIGB field 370 indicates that the currently receivedPPDU 300 is MU-MIMO transmitted. To the contrary, the STA may bedesigned so as not to decode the VHT-SGIB field 370 only in the case inwhich the common control information indicates that the currentlyreceived PPDU 300 is for a single STA (including the SU-MIMO).

The VHT-SIGB field 370 includes information on MCS for each STA andinformation on rate-matching. In addition, the VHT-SIGB field 370includes information indicating a length of the PSDU included in thedata field for each STA. The information indicating the length of thePSDU, which is information indicating a length of a bit sequence of thePSDU, may indicate the length in an octet unit. A size of the VHT-SIGBfield 370 may be changed according to a type of MIMO transmission(MU-MIMO or SU-MIMO) and a bandwidth of a channel used for transmissionof the PPDU.

The data field 380 includes the data that is intended to be transmittedto the STA. The data field 380 includes the PSDU which is the MPDUtransferred from the MAC layer, a service field for initializing thescrambler, a tail field including a bit sequence required to return aconvolutional encoder to a zero state, and padding bits forstandardizing the data field.

In the WLAN system as shown in FIG. 1, in the case in which the AP 10 isto transmit the data to the STA1 21, the STA2 22, and the STA3 23, itmay transmit the PPDU to the STA group including the STA1 21, the STA222, the STA3 23, and the STA4 24. In this case, as shown in FIG. 3, thespatial streams may be allocated so that the spatial streams allocatedto the STA4 24 are not present, and a specific number of spatial streamsmay be allocated to each of the STA1 21, the STA2 22, and the STA3 23,thereby transmitting the data. In an example as shown in FIG. 3, it maybe appreciated that a single spatial stream is allocated to the STA3 31,three spatial streams are allocated to the STA2 22, and two spatialstreams are allocated to the STA3 23.

FIG. 4 is a block diagram showing a format of a data field according tothe exemplary embodiment of the present invention.

Referring to FIG. 4, the data field 400 includes a service field 410, adata unit 420, padding bits 430, and a tail field 440.

The service field 410 may include a bit sequence for initializing thescrambler and a cyclic redundancy check (CRC) bit sequence calculatedfor a corresponding VHT-SIGB field transmitted to the receive STA. Aprocess of generating the service field in the transmit STA and adetailed structure of the service field will be described below indetail.

The data unit 420, which is a data unit transferred from the MAC layer,may be the PSDU. Lengths of the PSDUs may be different in each receiveSTA, and be different according to the transmitted spatial stream evenin the same receive STA. However, lengths of the PPDUs are the same aseach other in transmitting the PPDUs in the transmit STA. Therefore, itis required to set the lengths of the data fields to be the same as eachother. Therefore, the padding bits 430 are added to the data unit 420.Meanwhile, the padding bits 430 added to the data unit 420 may havelengths changed according to the lengths of the data units and may notbe added to some data units.

The tail field 440 may be included only in the case in which a bitsequence configuring the data field is encoded according to the BCCencoding scheme and may include a bit sequence used to make a BCCencoder a zero state. Since encoding schemes that may be supported ineach STA may be different and encoding schemes that is to be applied tothe data units transmitted to each STA may be different, the tail fieldmay be included in a data field for a specific STA and may not beincluded in a data field for another specific STA. Hereinafter, anexample of a method for transmitting a data unit through generation andtransmission of the PPDU will be described in detail.

FIG. 5 is a diagram showing an example of a method for transmitting adata unit based on a method for generating a PPDU according to theexemplary embodiment of the present invention.

Referring to FIG. 5, the MAC layer transfers a generated data unit, thatis, an MPDU or an A-MPDU to the PLCP sub-layer. In the PLCP sub-layer,the MPDU or the A-MPDU is called a PSDU. The PLCP sub-layer adds controlinformation to the PSDU. The control information is required totransmits the PSDU to another STA through the PHY layer and is requiredof the another STA to acquire data by receiving, demodulating anddecoding the corresponding PPDU. The corresponding control informationmay be included in the L-SIG field, the VHT-SIGA field, and the VHT-SIGBfield, and the tail field may be additionally added according to a typeof an encoder (in the case in which the encoder is a BBC encoder). Thecontrol information may be added in the PSCP sub-layer based on theTXVECTOR parameter transferred from the MAC layer to the PHY layer.

The TXVECTOR parameter may further include an information parameterindicating a bandwidth for transmission of a data unit in duplicatedformat applied to the PSDU and/or an information parameter indicatingwhether or not dynamic bandwidth operation is supported at the time oftransmission of the duplicated data unit. The bandwidth indicationinformation parameter indicates a transmission bandwidth, and abandwidth value may be set to 20 MHz, 40 MHz, 80 MHz, 160 MHz and/or80+80 MHz. The dynamic bandwidth indication information parameter may beset to indicate ‘Dynamic’ in the case in which the dynamic bandwidthoperation is supported and be set to indicate ‘Static’ in the case inwhich the dynamic bandwidth operation is not supported, which may beimplemented by 1 bit. In the case in which the dynamic bandwidthindication information parameter is set to a value indicating ‘Dynamic’,the receive STA may transmit a data unit responding to the data unit tothe transmit STA using the entirety or a portion of a channel bandthrough which the data unit is transmitted. On the other hand, in thecase in which the dynamic bandwidth indication information parameter isset to a value indicating ‘Static’, the receive STA may transmit aresponse data unit to the transmit STA using only a channel band throughwhich the data unit is transmitted. The use of the channel band meansthat the bandwidth indication information parameter of the TXVECTOR forthe response data unit is set to a corresponding bandwidth value and isused.

Meanwhile, the bandwidth indication information parameter and/or thedynamic bandwidth indication information parameter may be the basis fora procedure of generating a scrambling code for scrambling the datafield. This will be described below in more detail.

The following Table 2 shows a configuration of a TXVECTOR parameter.

TABLE 2 Parameter Associated Primitive Value Bandwidth IndicationPHY-TXSTART.request CBW20, CBW40, Information (TXVECTOR) CBW80, CBW160or (CH_BANDWIDTH_IN_NON_HT) CBW80 + 80 if any Dynamic BandwidthPHY-TXSTART.request Static or Dynamic Indication Information (TXVECTOR)if any (DYN_BANDWIDTH_IN_NON_HT)

The transmit STA adds the service field, the padding bit (if needed),and the tail bit (in the case of the BCC encoding) to the PSDU includingthe data that is to be transmitted.

The service field may include a bit sequence for initializing thescrambler and a cyclic redundancy check (CRC) bit sequence calculatedfor a corresponding VHT-SIGB field transmitted to the receive STA(however, the CRC bit sequence is calculated except for the tail bitincluded in the VHT-SIGB field). A format of the service field may berepresented by the following Table 3.

TABLE 3 Bits Field Description B0~B6 Scrambler Initialization Set to 0B7 Reserved B8~B15 CRC CRC calculated for VHT-SIGB Field (except forTail Bits)

The service field for the PPDU that may be used in the next generationWLAN system includes the CRC bit sequence calculated for the VHT-SIGBfield. On the other hand, since the VHT-SIGB field is not included inthe existing WLAN system, the CRC bit sequence is not included in theservice field. Therefore, the transmit STA needs to generate differentservice fields according to whether the PPDU format is the format usedin the next generation WLAN system or the format used in the existingWLAN system to add the generated service field to the PSDU. To this end,a service field information parameter which is an information parameterrelated to the service field is included in the TXVECTOR parameter, andthe transmit STA may be implemented to generate the service field basedon the service field information parameter. The following Table 4 showsthe service field information parameter included in the TXVECTORparameter.

TABLE 4 Transmission/Reception Parameter Condition Vector Applying ValueTXVECTOR RXVECTOR Service Format = Legacy Scrambler Initialization, YesNo Field 7 Null Bits + 9 Reserved Bits Format = High ScramblerInitialization, Yes No Throughput 7 Null Bits + 9 Reserved Bits Format =Very Scrambler Initialization, Yes No High Throughput 7 Null Bits + 1Reserved Bit + CRC Bits for VHT-SIGB Field

The transmit STA may generate the service field having the structure asshown in Table 3 based on the service field information parameterindicating the next generation WLAN system, that is, indicating the veryhigh throughput (VHT) format.

The transmit STA scrambles the added field and bits and the PSDU. Thescrambling performed by the transmit STA is based on the scrambling codegenerated by the transmit STA. A scrambling process will be describedbelow in more detail with reference to FIG. 6.

FIG. 6 is a diagram showing an example of scrambling according to theexemplary embodiment of the present invention.

Referring to FIG. 6, input data Data In is a bit sequence including theservice field, the PSDU, the padding bits, and the tail bits scrambledby the transmit STA. The transmit STA generates a scrambling sequencebased on an initial scrambling sequence and a generator polynomial. Inthe present example, the generator polynomial S(x) may be represented bythe following Equation 1.S(x)=x ⁷ +x ⁴+1  [Equation 1]

When the bandwidth indication information parameter is not included inthe TXVECTOR, the transmit STA may set the initial scrambling sequenceto a 7 bit pseudo random non-zero integer.

When the bandwidth indication information parameter is included in theTXVECTOR, the initial scrambling sequence may be set as shown in FIG. 7.

FIG. 7 is a diagram showing an example of an initial scrambling sequenceaccording to the exemplary embodiment of the present invention.

Referring to FIG. 7, in the case in which a bandwidth indicationinformation parameter CH_BANDWIDTH_IN_NON_HT is present in the TXVECTORparameter and a dynamic bandwidth indication information parameterDYN_BANDWIDTH_IN_NON_HT is not present in the TXVECTOR, the scramblingsequence includes a 5 bit pseudo random integer and a set value of thebandwidth indication information parameter. In the case in which thebandwidth indication information parameter is set to a value (CBW20)indicating 20 MHz, the 5 bit pseudo random integer may be set to a 5 bitpseudo random non-zero integer. In the case in which the bandwidthindication information parameter is set to a value other than the value(CBW20) indicating 20 MHz, the 5 bit pseudo random integer needs not tobe the 5 bit pseudo random non-zero integer.

In the case in which both of the bandwidth indication informationparameter and the dynamic bandwidth indication information parameter arepresent in the TXVECTOR parameter, the scrambling sequence includes a 4bit pseudo random integer, a set value of the dynamic bandwidthindication information parameter, and a set value of the bandwidthindication information parameter. In the case in which the bandwidthindication information parameter is set to a value (CBW20) indicating 20MHz and the dynamic bandwidth indication information parameter is set toa value indicating ‘Static’, the 4 bit pseudo random integer may be setto a 4 bit pseudo random non-zero integer. In the case other than theabove-mentioned case, the 4 bit pseudo random integer needs not to bethe 4 bit pseudo random non-zero integer.

The following Table 5 and Table 6 show examples of the set values of thebandwidth indication information parameter and the dynamic bandwidthindication information parameter.

TABLE 5 Enumerated Value Set value CBW20 0 CBW40 1 CBW80 2 CBW160 orCBW80 + 80 3

TABLE 6 Enumerated Value Set value Static 0 Dynamic 1

Meanwhile, in the bandwidth indication information parameter, the leastsignificant bit (LSB) among bits that are set values of the informationparameters is first transmitted. For example, in the case in which thebandwidth indication information parameter is set to a value indicatingCBW80, it may be represented by ‘1 0’. In this case, B5 of the initialscrambling sequence is set to 0, and B6 thereof is set to 1.

As shown in FIGS. 6 and 7, the transmit STA may generate the initialscrambling sequence based on the bandwidth indication informationparameter and the dynamic bandwidth indication information parameter ofthe TXVECTOR parameter and generate the scrambling sequence based on theinitial scrambling sequence and the generator polynomial. The transmitSTA perform the scrambling based on the scrambling sequence. Thetransmit STA scrambles the input data based on the scrambling sequenceto output the scrambled data (scrambled data out).

Again referring to FIG. 5, the transmit STA encodes the scrambled addedbits and the PSDU according to a specific encoding scheme. As theencoding scheme, the BCC encoding scheme or the LDPC encoding scheme maybe applied. A concept of including the scrambled encoded PSDU and thefield/bits added thereto may called a coded-PSDU (C-PSDU). The C-PSDUmay be called a data field.

The PLCP sub-layer may further add a training symbol in order tosynchronize wireless resources, acquire timing, and acquire antennadiversity between a transmit end AP and/or STA and a receive end STA.This may be implemented by adding legacy training symbols including theL-STF and L-LTF for the L-SAT and VHT training symbols including theVHT-STF and VHT-LTF for the VHT-STA. The PPDU transmitted through thewireless resource is mapped to an OFDM symbol and transmitted throughthe wireless resource. Here, the PPDU mapped to the OFDM symbol and/orthe data field included in the PPDU may be implemented to have aspecific bit size and be implemented to be a multiple of octet throughthe padding bit sequence added to the PSDU. The generate PPDU may bemapped to the OFDM symbols and then transmitted to at least one MIMOpaired target STAs.

FIG. 8 is a diagram showing an example of a method for receiving a PPDUgenerated according to the exemplary embodiment of the presentinvention.

Referring to FIG. 8, the receive STA starts to receive the VHT trainingsymbol and the VHT-SIGB field based on the L-SIG field and the VHT-SIGAfield.

The receive STA does not decode the VHT-SIGB field when the group ID ofthe VHT-SIGA field indicates the SU-MIMO. On the other hand, the receiveSTA decodes the VHT-SIGB field when the group ID of the VHT-SIGA fieldindicates the MU-MIMO. When the VHT-SIGB field is decoded, the receiveSTA confirms the CRC bit sequence of the service field to confirmwhether or not abnormality is present in the CRC.

Then, a terminal receives, decodes, and descrambles the C-PSDU. Thedecoding of the C-PSDU is performed corresponding to encoding schemeindication information included in the VHT-SIGA field. The descramblingof the C-PSDU may be performed corresponding to the applied scramblingsequence.

Meanwhile, the receive STA may set a specific bit value of an initialscrambling sequence which is first 7 bits of the scrambling sequence tothe bandwidth indication information parameter and/or the dynamicbandwidth indication information parameter of the RXVECTOR which is thereceiving information parameter. This may correspond to animplementation of FIG. 7 which is a relationship between the bandwidthindication information parameter and the dynamic bandwidth indicationinformation parameter of the TXVECTOR and the scrambling sequence.

When the C-PSDU is decoded and descrambled, the PSDU which is the dataunit including the data may be acquired. Through this process, thereceive STA may normally receive the data unit.

According to the above-mentioned exemplary embodiment, in the nextgeneration WLAN system extended to a wider band, the channel bandwidthrelated information and the support indication information of thedynamic bandwidth operation are through the scrambling sequence, but notbeing implemented in a separate signal field. Therefore, it is possibleto support transmission and reception using a wide bandwidth,transmission and reception of a data unit in duplicated format, and/ortransmission and reception of a dynamic bandwidth without using thesignal field short due to a large amount of information required tosupport the MU-MIMO. In addition, the initial scrambling sequence, whichmay be used even in the existing WLAN system, may secure backwardcompatibility.

Further, in the above-mentioned exemplary embodiment, the informationparameter related to the implementation of the service field isadditionally included in the TXVECTOR parameter, whereby the transmitSTA may accurately generate the service field appropriate for the PPDUformat of the WLAN system supporting the MU-MIMO. This reduces thepossibility that an error such as a failure of an exchange of the dataunit between the transmit and receive STAs occurs, thereby making itpossible to secure communication having higher reliability.

FIG. 9 is a block diagram showing a wireless apparatus to which theexemplary embodiment of the present invention may be implemented.

Referring to FIG. 9, the wireless apparatus 900 includes a processor910, a memory 920, and a transceiver 930. The transceiver 930 includes aphysical (PHY) unit 931 and a media access unit (MAC) unit 932,transmits and/or receives a wireless signal, and implements a PHY layerand an MAC layer of the IEEE 802.11. The processor 910 is functionallyconnected to the transceiver 930 and is set to implement the MAC layerand/or the PHY layer implementing the exemplary embodiment of thepresent invention related to the transmission and reception of the dataunit through the generation of the PPDU and shown in FIGS. 4 to 8. Inaddition, the processor 910 is set to control a set of the TXVECTORparameters.

The processors 910 and/or the transceiver 930 may include anapplication-specific integrated circuit (ASIC), other chipsets, logicalcircuits, and/or data processing apparatuses. When the exemplaryembodiment is implemented by software, the above-mentioned method may beimplemented by a module (a process, a function, or the like) thatperforms the above-mentioned function. The module may be stored in thememory 920 and be performed by the processor 910. The memory 920 may beincluded inside the processor 910 and may be separately positionedoutside the process 910 and be functionally connected to the processor910 by widely known various units.

As set forth above, according to the exemplary embodiments of thepresent invention, in the next generation WLAN system supportingtransmission in a wider band, the channel bandwidth related informationand the support indication information of the dynamic bandwidthoperation are not implemented in the signal field, but may beimplemented by setting the scrambling sequence. Therefore, it ispossible to support transmission and reception of the data frame using awide bandwidth, transmission and reception of the data frame includingthe data unit in duplicated format, the dynamic bandwidth operationwithout allocating signal field short due to a large amount ofinformation required to support the MU-MIMO. To this end, the setinitial scrambling sequence, which may be used even in the existing WLANsystem, may secure backward compatibility.

Further, in the above-mentioned exemplary embodiment, the informationparameter related to the implementation of the service field isadditionally included in the transmission information parameter(TXVECTOR), whereby the transmit STA may accurately generate the servicefield appropriate for the frame format of the WLAN system supporting theMU-MIMO. This reduces the possibility that an error such as a failure ofan exchange of the data frame between the transmit and receive STAs willoccur, thereby making it possible to secure communication having higherreliability.

What is claimed is:
 1. A wireless device of transmitting a data frame ina wireless local area network, the wireless device comprising: a mediaaccess control (MAC) unit configured to generate a data frame; aphysical (PHY) unit configured to transmit a wireless signal of the dataframe; and a processor being operably coupled to the MAC unit and thePHY unit and controlling a set of Transmission Vector (TXVECTOR)parameters, wherein the processor is configured for generating the setof TXVECTOR parameters, the set of TXVECTOR parameters including aservice field TXVECTOR parameter; generating a data unit, the data unitincluding a data field having a service field and a very high throughputsignal field (VHT-SIG-B), the service field including a scramblerinitialization field, a reserved field and a cyclic redundancy check(CRC) field, the VHT-SIG-B including a length field and a tail field;and transmitting a wireless signal of the data unit via an operatingchannel bandwidth, wherein the data field is scrambled with a scramblingsequence, and the scrambling sequence is generated based on an initialscrambling sequence and a generator polynomial, wherein the servicefield is determined based on the service field TXVECTOR parameter andthe VHT-SIG-B, and wherein the CRC field is set to CRC bits calculatedbased on the VHT-SIG-B excluding tail bits of the tail field.
 2. Thewireless device of claim 1, wherein the set of TXVECTOR parametersfurther includes a format TXVECTOR parameter indicating a format of thedata unit, wherein if the format TXVECTOR parameter indicates the formatof the data unit as very high throughput (VHT), the scramblerinitialization field includes 7 zero bits, and the reserved fieldincludes a reserved zero bit.
 3. The wireless device of claim 1, whereinthe initial scrambling sequence includes operating channel bandwidthinformation and a pseudo random integer, the operating channel bandwidthinformation indicating the operating channel bandwidth.
 4. The wirelessdevice of claim 3, wherein the initial scrambling sequence furtherincludes dynamic bandwidth information indicating whether a dynamicbandwidth operation is supported.
 5. The wireless device of claim 4,wherein the operating channel bandwidth information has 2 bits.
 6. Thewireless device of claim 5, wherein the 2 bits indicates one among 20MHz, 40 MHz, 80 MHz, contiguous 160 MHz and non-contiguous 80+80 MHz forthe operating channel bandwidth.
 7. The wireless device of claim 1,wherein the initial scrambling sequence has 7 bits.
 8. The method ofclaim 7, wherein the generator polynomial is represented by the belowformula,S(x)=x ⁷ +x ⁴+1, wherein S(x) is the generator polynomial, and x is avariable.
 9. A method for transmitting a data frame in a wireless localarea network, the method comprising: generating a set of TransmissionVector (TXVECTOR) parameters, the set of TXVECTOR parameters including aservice field TXVECTOR parameter; generating a data unit, the data unitincluding a data field having a service field and a very high throughputsignal field (VHT-SIG-B), the service field including a scramblerinitialization field, a reserved field and a cyclic redundancy check(CRC) field, the VHT-SIG-B including a length field and a tail field;and transmitting a wireless signal of the data unit via an operatingchannel bandwidth, wherein the data field is scrambled with a scramblingsequence, the scrambling sequence is generated based on an initialscrambling sequence and a generator polynomial, wherein the servicefield is determined based on the service field TXVECTOR parameter andthe VHT-SIG-B, and wherein the CRC field is set to CRC bits calculatedbased on the VHT-SIG-B excluding tail bits of the tail field.
 10. Themethod of claim 9, wherein the set of TXVECTOR parameters furtherincludes a format TXVECTOR parameter indicating a format of the dataunit, wherein if the format TXVECTOR parameter indicates the format ofthe data unit as very high throughput (VHT), the scramblerinitialization field includes 7 zero bits, and the reserved fieldincludes a reserved zero bit.
 11. The method of claim 9, wherein theinitial scrambling sequence includes operating channel bandwidthinformation and a pseudo random integer, the operating channel bandwidthinformation indicating the operating channel bandwidth.
 12. The methodof claim 11, wherein the initial scrambling sequence further includes adynamic bandwidth information indicating whether a dynamic bandwidthoperation is supported.
 13. The method of claim 12, wherein theoperating channel bandwidth information has 2 bits.
 14. The method ofclaim 13, wherein the 2 bits indicates one among 20 MHz, 40 MHz, 80 MHz,contiguous 160 MHz and non-contiguous 80+80 MHz for the operatingchannel bandwidth.